Embed UIViewController Programmatically?

You can do this by programmatically, below is the method which will take a bool value to make decision which view controller need to be added in container view and then will instantiate an object and after that will add it to containerView

- (void)addViewControllerToContainerView:(BOOL)addVC1
{
// Get storyboard
UIStoryboard *storyBoard = [UIStoryboard storyboardWithName:@"<name of storyboard>" bundle:[NSBundle mainBundle]];
    UIViewController *viewController = nil;
    if (addVC1)
    {
// get viewController with identifier 
        viewController = [storyBoard instantiateViewControllerWithIdentifier:@"<View Controller 1 Identifier>"];
    }
    else
    {
        viewController = [storyBoard instantiateViewControllerWithIdentifier:@"<View Controller 2 Identifier>"];
    }
// lets add it to container view
    [viewController willMoveToParentViewController:self];
    [self.view addSubview:viewController.view];
    [self addChildViewController:viewController];
    [viewController didMoveToParentViewController:self];
// keep reference of viewController which may be useful when you need to remove it from container view, lets consider you have a property name as containerViewController
    self.containerViewController = viewController;
}

When you need remove view controller from container view controller you can do this

   [self.containerViewController willMoveToParentViewController:nil];  // 1   
   self.containerViewController.view removeFromSuperView];
   [self.containerViewController removeFromParentViewController];//this line is updated as view is removed from parent view cotnroller istead of its viewcontroller is removed from parentViewController 
   self.containerViewController = nil

Apple docs about container view controllers